The basic architecture of a computing device is known to include a central processing unit ("CPU"), system memory, input/output ports, an address generation unit ("AU"), program control circuitry, interconnecting buses, audio-processing circuitry, and video processing circuitry. As the technology of the computing device elements continues to advance, computing devices are being used in more and more commercial applications. For example, computing devices are used in video game players, personal computers, works stations, video cameras, video recorders, televisions, etc. The technological advances are also enhancing video quality, audio quality, and speed at which computing devices can process data. The enhancement of the video quality is a direct result of video graphic circuit evolution.
Video graphic circuits have evolved from providing simple text and two-dimensional images to relatively complex three-dimensional images. Such evolution began with high-end computers such as workstations, where the use of complex and costly circuitry is more commercial viable. For example, anti-aliasing started with high-end computers. In general, anti-aliasing is a technique that visually compensates for jagged edges of video displayed images that result because of the finite size of pixels. The visual compensation begins by creating subpixel masks for each object that is to be drawn within a pixel. The resulting subpixel masks for a pixel are then processed to produce pixel information for the given pixel. For example, assume that three objects are partially contained within a pixel. The first object has twenty-five percent (25%) coverage of the pixel. The second object has thirty percent (30%) coverage of the pixel. The third object has twenty-five percent (25%) coverage of the pixel. The remaining twenty-percent (20%) of the pixel is covered by background information. Each object, including the background, contributes to the pixel information of the pixel based on their respective percentages.
The process of generating subpixel masks and the resulting processing of the subpixel masks have been discussed in several prior art references such as "A New Simple and Efficient Anti-aliasing with Subpixel Masks," by Andreas Schilling, et. al., Computer Graphics, Volume 25, Number 4, July 1991, and "The A-buffer, an Anti-aliasing Hidden Surface Method," by Loren Carpenter, Computer Graphics, Volume 18, Number 3, July 1984. While each of these references discusses a viable means for producing anti-aliasing, the schemes were not designed in terms of optimizing memory.
As is generally known, the amount of memory required for any processing device directly affects the cost of the processing device. Thus, the more memory requirements can be reduced, the more inexpensively the processing device can be produced. To make anti-aliasing commercially viable to the general public, the cost of video graphic processing circuits needs to be reduced by reducing the memory requirements. Therefore, need exists for a commercially viable three-dimensional video graphics processing method and apparatus that includes video anti-aliasing.